World War II bombing raids in London and Berlin struck the edge of space, our new study reveals

Patrick Major, University of Reading and Chris Scott, University of Reading

The bombing campaigns of World War Two left an indelible mark on the world’s towns and cities and in the memories of the people who survived them. In a new study, we found that the most destructive war in history also made its mark in our atmosphere.

In an age when long-term monitoring of the environment is increasingly important, scientists are turning to historical datasets for clues in solving present-day science puzzles.

One such dataset is the unique record of the Earth’s ionosphere – the electrified region of the Earth’s upper atmosphere, which was painstakingly recorded from 1933 onwards at the Radio Research Station near Slough.

Scientists at the RRS were monitoring the ionosphere as it was then vital for long-distance radio communications. Shortwave radio is reflected by the ionosphere and allows the signal to be transmitted long distances over the horizon.

They had noted that the density of the ionosphere was extremely variable and had set up the monitoring station in order to look for patterns in this variability. Much of this is due to changes in solar activity.

The ionosphere is created when x-rays and extreme ultraviolet light from the sun are absorbed by our atmosphere, electrifying it. We now know, thanks to a fleet of spacecraft monitoring the sun, that not all of this variability can be explained by solar activity. Attention is increasingly turning to sources from the lower atmosphere and the ground.

But where to find ground events capable of leaving a signature at the edge of space? The answer lies in the past. World War Two witnessed an explosive arms race, which culminated, in its most extreme form, in the atomic bomb.

But most